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• Record audio data to an existing media file using FFMPEG API

  3 février 2021, par bbdd

  My task is to record the received audio data in a media file. I have no problem with this, everything works fine. But, when closing the audio file, I will no longer be able to re-open it and write the audio data to the end of the audio file. How do I solve this problem ? And in general, is it possible to write new data to the end of an existing media file ?

  


  This is a piece of code where I record the trailer and close the media file :

  


  // Writing the stream trailer to an output
// media file and free the file private data.
av_write_trailer(p_oFrmCtx);
avformat_close_input(&p_oFrmCtx);



  


• Convert streaming MPEG-4 raw data to H.264

  16 août 2012, par Jonathan Hawkes

  I've got a Sony network camera (SNC-RZ25N) that I am trying desperately to get data from in some meaningful format. The documentation says it sends MPEG-4 raw data, but is not more specific than than. I can capture a segment of the stream using curl ( http://techhead.biz/media/tsv.m4v ) and it will play using VLC and ffplay (though it plays too fast in ffplay).

  After a day and a half of tinkering, I just discovered that I cannot use ffmpeg to convert this stream directly. For one, the only way ffmpeg accepts piped data as input (that I'm aware of) is in the 'yuv4mpegpipe' format.

  I tried piping to ffmpeg using 'm4v' as the specified format, but it seems to want to read the entire stream before it begins processing.

  Anyone know how I can do this ? Using commandline tools ? Open source libraries in ANY programming language ? Simpler solutions are preferred, but any working solution would be great.

• avformat/matroskaenc : Don't use stream side-data size

  21 mai 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Don't use stream side-data size
  av_stream_get_side_data() tells the caller whether a stream has side
  
  data of a specific type ; if present it can also tell the caller the size
  
  of the side data via an optional argument. The Matroska muxer always
  
  used this optional argument, although it doesn't really need the size,
  
  as the relevant side-data are not buffers, but structures. So change
  
  this.
  Furthermore, relying on the size also made the code susceptible to
  
  a quirk of av_stream_get_side_data() : It only sets the size argument if
  
  it found side data of the desired type. mkv_write_video_color() checks
  
  for side-data twice with the same variable for the size without resetting
  
  the size in between ; if the second type of side-data isn't present, the
  
  size will still be what it was after the first call. This was not
  
  dangerous in practice, as the check for the existence of the second
  
  side-data compared the size with the expected size, so it would only be
  
  problematic if lots of elements were to be added to AVContentLightMetadata.
  Reviewed-by : James Almer <jamrial@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c